Embedded Linux -...

1Email : simhkeng@yahoo.com

Part 2

Embedded Linux

By : H K Sim(Contact Email : simhkeng@yahoo.com)

March 2007

7.0 Embedded Linux Platform

On RISC Processor

Why use embedded Linux

� Embedded application is getting more complex and thus need more

powerful operating system

� Free license O.S. is needed to reduce product cost. Network equipments

such as Switches, routers , wireless access points, cellular phones,

automation server, … uses embedded Linux. Across all markets and

technologies

� Ethernet network port ( IP enable device ) required (instead just Serial port)

� More external data storage required

� mature , high performance, large applications, networking protocol

available

� large number of active developers sharing their experiences

� Good for research activities. Able to add/modify Operating System at

kernel and driver level to achieve performance requirement ( OS source

code is available )

� royalty free

Embedded OS & Market Share

http://www.linuxdevices.com/articles/AT7070519787.html

Linux support what processor chip?

Processors that Linux supported

�Intel Pentium

�Freescale PowerPC ( 4th generation )

�MIPS architecture ( BCM 1250 Network processor )

�ARM architecture

�Intel ARM XScale ( network processor IXP425.. Etc)

… more coming

Embedded system expectation

� Contain a micro- processor, flash memory, DRAM … others

� Design to a specific application ( not general purpose computing )

� Simple user interface (Not GUI) via serial port – normally

� Limited resource ( small program & data memory, no monitor, no hard

disk )

� Communicate with outside world via serial interface ( RS232/485 ),LAN

/ Wireless, USB, LED, general purpose I/O

� Reset button

Typical Development setup

Eth0Eth1

Minicom

Serial port to communicate with embedded board

LAN to upload Linux OS image or application program

Embedded boardDevelopment Linux PC

Window HyperTerminal

Choose a off-the-shelf embedded Linux Board How-to

� Hardware consideration

- CPU speed for a typical application

- external interface : serial , Ethernet port, USB, wireless,

memory

� Software tools consideration

- working cross- compiler, linker and make file with your hardware

- lot of software examples for application

- able to download program to board via FTP

� System feature consideration

- default factory setting ( useful when enter into endless loop )

- system stability

- monitor program ( usually using serial port ) available

Why choose A-LinEmb Development Board

� Careful select Hardware system that can demonstrate the complete concept of

cross-platform Linux Embedded system

� Hardware consideration

- 100MIPS , 32 bits RISC Processor

- more than two serial ports - one use for system Monitoring

- two LAN ports - able to download program via FTP

- 1 USB – able to extend system memory using USB memory stick

� Software consideration

- working cross- compiler, linker and make file to build your kernel and

image file

- able to upload image file, fimage, and application program to board via FTP

- provide web server

� System feature consideration

- default factory setting ( useful when enter into endless loop )

- stable system

- monitor program ( usually using serial port ) available

A-LinEmb Development Setup

Development Linux PC

Cross-compiled application FTP to embedded board

Serial port to communicate to the embedded board

Serial portsUSB

Close look at A-LinEmb board

Embedded Linux CPU

RISC processor

Power circuit

Battery for RTC

A-LinEmb Board

COM1COM2

Eth0Eth1

COM1COM2

Eth0Eth1

Acquisition

Application Example of A-LinEmb board

� Before you setup Embedded Linux system, you can use Serial port , on

Window PC ( Hyper Terminal ) or Linux PC ( minicom) to view the

structure of the A-LinEmb system

A-LinEmb Monitor Program ( Window )

� Go to Window Hyper Terminal, set the following :

A-LinEmb Development Overview

Set up Linux PC( Fedora core 2)

Install A-LinEmb SDK

Make customize Linux OS image file

fimage

ftp fimage toA-LinEmb

Create applicationsOn Linux PC

ftp application toA-LinEmb

Cross-compile& create executable Program for A-LinEmb

3rd party development

SDK – very expensive

� Install Linux OS on the development PC - Fedora 2 & above

� Install board vendor’s development system on the same PC

� Configure Linux OS function and build your own Linux OS image file

� FTP Linux OS file to A-LinEmb

� Develop application program on Linux development PC

� Debug and test the application program at PC level

� When ready, cross-compile/link and create an executable file in A-Emb’s

architecture

� FTP the application program to the board’s user memory

� Run the program in the A-LinEmb’s environment and verify it works

A-LinEmb Development Overview

�A compiler that run on one computer architecture( i.e i386 )

but generate executable code that can run on computers with

different architecture ( Arm, MIPS …etc )

�Cross compiler is hardware architecture dependent

�CRIS ,acronym 'Code Reduced Instruction Set‘, cross

compiler is used in A-LinEmb

What is Cross Compiler ?

A-LinEmb Board SDK Setup

A-LinEmb development tool chain installation requirement

� Install new pmake version 1.45-16

Pmake-1.45-16.i386.rpm

A-Emb board need pmake 1.45-16 to work with the cross-compiler

(Fedora core2’s pmake is verion 1.45-14)

� Install cross-compiler

Cris-dist-1.63-1.i386.rpm

� Install SDK release 2.01

Devboard-R2_01.tar.gz

Devboard-R2_01-distfiles.tar.gz

� Create a folder in /root/axis and contain the following files

Cris-dist-1.63-1.i386.rpm

Pmake-1.45-16.i386.rpm

Devboard-R2_01.tar.gz

Devboard-R2_01-distfiles.tar.gz

Development Environment Setup in /root/axis

� Step 1 install pmake

# rpm –Uvh pmake-1.45-16.i386.rpm

� Step 2 Install Cross Compiler

# rpm –Uvh cris-dist-1.63-1.i386.rpm

� Step 3 – install Software Development System ( SDK) Release 2.01

tar xvfz devboard-R2_01.tar.gz to create devboard-R2_01 folder

tar xvfz devboard-R2_01-distfiles.tar.gz to create distfiles is then created.

� Step 4 – go to the just created folder devboard-R2_01

- symbolic link inside the devboard-R2_01 folder pointing to this distribution

folder using : ln –s ../distfiles

� Go to folder /root/axis/devboard-R2_01

� to define what kind of board you are using

. /install

� Configuration

make xconfig

select Linux 2.6x and others option and save configuration

� Install all packages needed for the configuration

./configure

� Build Linux OS Image

a file called fimage should be created if no error occur

Create A-LinEmb custom Linux OS

� flash the created fimage file to the development board using ftp

� While in folder /root/axis/devboard-R2_01 on the development PC

Create A-Emb custom Linux OS

10.20.100.87255.255.255.0

10.20.100.90255.255.255.0

e same

ork domain

]# ftp 10.20.100.87

> binary

> hash - display flashing progress status

> put fimage flash

…….. flashing in progress …….

> quit

� All A-LinEmb application folders will put in the path /root/axis/devboard-

R2_01/apps/<myprogram1>

� Make A-LinEmb application program

Convert a xxx.c file from fedora2 platform to custom board platform

Go to folder devboard-R2_01

. init_env

Go to /root/axis/devboard_R2-01/apps/<myprogram1>

first create a make file for program myprogram.c on A-LinEmb architecture

( see next page for detail )

make cris-axis-linux-gnu

� FTP application to embedded board

Repeated process for new application

Cross-compile A-LinEmb Board Application Software

A-LinEmb make file for CRIS Compiler

AXIS_USABLE_LIBS = GLIBC UCLIBC

include $(AXIS_TOP_DIR)/tools/build/Rules.axis

PROGS = myprogramINSTDIR = $(prefix)/bin/

INSTMODE = 0755

INSTOWNER = root

INSTGROUP = root

OBJS = myprogram.o

all: $(PROGS)

$(PROGS): $(OBJS)

$(CC)$(LDFLAGS) $^ $(LDLIBS) -o $@

install: $(PROGS)

$(INSTALL) -d $(INSTDIR)

$(INSTALL) -m $(INSTMODE) -o $(INSTOWNER) -g $(INSTGROUP) $(PROGS)

$(INSTDIR)

clean: rm -f $(PROGS) *.o core

Two area need to change

Software Knowledge for embedded Linux development

� Prefer to use most basic C language ( to be transportable

to all platform)

� Need to familiar with Linux system & commands

� Need to know Linux programming using C language

� For hardware related programming :

- Serial port

- Socket programming – for network programming

- USB flash memory – for removable data storage

Some Practical Issues

�Hardware ( Chip/Board level ) vendor do not have

control on software due to outsourcing to 3rd party

�Need to pay 3rd party for software development tools ,

possible license per product shipped

�Vendor’s Linux development platform is different from

your Linux development platform

vendor uses redhat9 but you use Fedora core 2

�Even with same platform, the kernel version number

must also be the same to minimize error

�Vendor application( specific purpose ) example is not

available , need lot of resources to research how to do it

… other ?

8.0 A-LinEmb Board - How to

Reset to Factory Default

� Reset to factory default setting will be carried out when the A-LinEmb go

into a stage that it “hang up” and re-power-up the product has no effect.

� Insert a small pin to the hole at front panel. Power up the A-LinEmb

while the button inside the hole still un-release. The front orange color will

both on and then one-on and one-off indicate that it is loading the default

Linux OS. You can then release the button and wait for the process to

complete.

this process can be monitored as long as your serial port is connected to to

� After the loading of default factory setting, you have to FTP your own

fimage file to get back your original setting.

� After the default setting is loaded, the network ports has the following

setting:

Eth0 : IP= 192.168.0.90 mask = 255.255.255.0 Bcast = 192.168.0.255

Eth1 : IP= 10.0.0.90 mask = 255.0.0.0 Bcast = 10.255.255.255

� Assuming the Linux development PC is connected to eth0, now you have to

temporary change your PC’s IP address to be in he same network domain

e.g. IP address: 192.168.0.1 mask: 255.255.255.0 Bcast: 192.168.0.255

� Do a ping from Linux development PC to A-LinEmb to ensure is linked

� Use flash fimage procedure to update the A-LinEmb OS

� Now you can use the browser on your development PC to edit the

/etc/conf.d/net.eth0 and /etc/conf.d/net.eth0 files to set your new IPs

� Do not forget to change back your development PC’s IP so that they are in

the same network domain

A-LinEmb Editors

� Web based Editor

This is the best editor to use to change the content of an existing file .

e.g /etc/conf.d/ xxx configuration file. It can not be use to create new

files. The editor name is called editcgi and is reside in the web server.

From your PC’s web browser use http://<A-LinEmb’s IP address> will

start the web based editor. You can edit, save, browse the files on the

A-LinEmb device

� Serial port , COM1 (not COM2) access editor

This is the simplified version of the standard Linux editor such as :

vi editor – default with the Linux OS

easyedit ( preferred ) – need to configure to include

(Note : on Linux development PC , gedit which is very user friendly )

� At startup, use LAN eth0 , http://10.20.100.87 and go into the root directory

A-LinEmb File Structure – / root folder

Link to the flash

memory where

read/write is available

IP address of eth0

� In /mnt folder

Link to the USB

memory stick

On-board flash

where user

application is kept

A-LinEmb File Structure - /mnt folder

� At startup, use LAN eth0.

� /etc/conf.d - all the network configuration files

A-LinEmb Network Configuration – /etc/conf.d

� /etc/init.d - initialization configuration folders

A-LinEmb File System Initialization– /etc/init.d

A-LinEmb Device Parameters

� Parameters that can be altered

IntelligentNetwork device

Mac address

IP address

( fix IP or DHCP client )

Device Name

( Host Name )

Web Server ( BOA)

Time & date

USB memory

Login name

COM port

USB Memory Stick ( use Kernel 2.6 )

� How to use USB memory stick ?

- in folder /etc/init.d, create a file called bootmisc.sh

- change the file permission to 755 using :

chmod 755 bootmisc.sh

- inside file bootmisc.sh , insert the following lines :

#!/bin/sh

mount -t vfat /dev/sda1 /mnt/1

- edit the file /etc/init.d/rc , add the line to the end of file./etc/init.d/bootmisc.sh just before “ exit 0 “

now when you write data to folder /mnt/1 will be automatically write

to the usb memory stick

Change network related parameters

� Change network related items, mac address, IP address

� In folder /etc/conf.d , edit the following files

- Hostname- mac - net.eth0 - net.eth1

to change the network parameters

� host name :

HOSTNAME="axis-00408c6e14ae"

� Mac address :

MAC="00:40:8C:6E:14:AE“

� net.eth0 / net.eth1

# MAC="00:40:8C:CD:00:00"

#BOOTPROTO=‘dhcp”

BOOTPROTO="none“

DHCP_CLIENT="/sbin/udhcpc -i eth0"

MEDIA="auto"

…# If you are using DHCP the following variables will not be used.

IP="10.20.100.87"

NETMASK="255.255.255.0"

BROADCAST="10.20.100.255"

GATEWAY="10.20.100.10"

Change network related parameters

WebServer ( http server )

� A-LinEmb board uses Boa linux web server, is a smaller version of web

server compare with Apache Web server.

� The factory default configuration has only html folder and do not have the

CGI ( Common Gateway Interface ) folder

� To configure the Boa server, go to file /etc/httpd/conf/boa.conf using web

browser or monitor program

Customize your own web server

Design condition :

� Location of user web folder is in /mnt/flash/userweb

� Inside the userweb folder, there are 2 folders : html and cgi

� /mnt/flash/userweb/html folder keep all html files include start-up

webpage . i.e http://<A-LinEmb IP address> will activate this page

Start-up page name is : index.html

� /mnt/flash/userweb/html folder keep all the non-html program such as CGI

and others

� When http://<A-LinEmb’s IP address> will activate the index.html

� When http://<A-LinEmb’s IP address>/cgi/mycgi.cgi will run the cgi

program called mycgi.cgi

� Go to /mnt/flash/userweb

folder, create two folders

named : cgi & html

� Go to /etc/httpd/conf folder ,

edit the boa.conf

� Using monitor program via serial port, go to /mnt/flash, use mkdir to create a

folder called userweb

/mnt/flash/userweb

/html /cgi

myhtml.html Editcgi.cgi

For this case may not be necessary as the path is the same as browser path

index.html

http://10.20.100.87/

<html>

<head>

<title>Linux Experience Sharing</title>

</head>

<h1><b>Sharing of Linux development Experience</h1></b><br>

To Bwowse/Edit/Save of files ( or http://IPaddress/cgi/editcgi.cgi)

<a href="/html/myhtml.html"> View myhtml.html </a>

</body>

</html>

Change System Date & Time

� Change the date and time on A-LinEmb board

#] date MMDDHHMMYYYY

e.g. date 030110452006

Your will then be replied with a understandable date/time format

To save it permanently, use :

#] hwclock –w

� Does the A-LinEmb Network port’s LED works ?

the A-LinEmb’s network port LEDs will not lighted up when the LAN

cable is inserted and linked to the network Switch. You should see

from the network Switch’s LED to know the link is established or not.

only Power-on LED ( Green ) will turn on

� How to re-initialize the system at command prompt.

]# init 0 or ]#init 6 for A-LinEmb board only

note : when mode change, system will reboot

� Can I create new folder using web editor ( editcgi) ?

No. folder can only be created when you are in monitor mode using

command ]# mkdir <folder name>

� Which area I can save my programs ?

the area that user can save their program or configuration files is in

/mnt/flash. The default folder in this directory is /mnt/flash/etc which

store all the configuration and is link to /etc as shown below

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